A lot of injection molded articles, for example plastic preforms of the variety that are for blow molding into beverage bottles, require extended cooling periods to solidify into substantially defect-free molded articles. To the extent that the cooling of the molded article can be effected outside of the injection mold by one or more so-called post-mold devices, the productivity of the injection mold may be increased (i.e. by reducing the cycle time). A variety of such post-mold devices, and related methods, are known and have proven effective in optimizing, i.e. reducing, the injection molding machine cycle time.
In a typical injection molding system a just-molded, and hence only partially cooled, molded article is ejected from the injection mold and into a post-mold device, commonly known as a take-out device or end-of-arm-tool (EOAT), having a plurality of cooled carriers (otherwise known as a cooling tube, take-out tube, cooling sleeve, amongst others) for post-mold cooling of the molded article outside of the mold.
U.S. Pat. No. Re. 33,237 describes a post-mold device for removing partially cooled injection molded preforms from the core side of an injection mold. The preforms are ejected from the mold directly into cooled carriers (such as that described in commonly assigned U.S. Pat. No. 4,729,732), and transported by the post-mold device to an outboard position adjacent the mold. The post-mold device may include multiple sets of carriers to accommodate multiple sets of preforms (i.e. multiple shots or batches of preforms).
Commonly assigned U.S. Pat. No. 6,171,541 describes another post-mold device that includes a set of cooling pins for insertion into the interior of a partially cooled preform, the preform arranged in a cooled carrier of a first post-mold device, to discharge a cooling fluid therein. An example of the foregoing is sold under the trade name of COOLJET, a trade-mark of Husky Injection Molding Systems Limited.
Commonly assigned U.S. Pat. No. 7,104,780 describes a post-mold device similar to that of the '541 patent further including molded article pickers for removal of the preform from the cooled carrier of the first post-mold device. The molded article picker includes a pin operable to cooperate with a vacuum source to evacuate a volume defined within the preform to cause the preform to remain therewith as the molded article picker is moved away from the carrier. The second post-mold device, mounted to a frame, may be rotated by 90 degrees to a discharge position and the vacuum to the molded article pickers may be terminated to allow the preforms to fall off the pins.
An example of the foregoing post-mold device is sold under the trade name of COOLPIK, a trade-mark of Husky Injection Molding Systems Limited. The molded article picker of the second post-mold device further includes a sealing surface disposed on a front face of a tooling plate to sealingly cooperate with a front face of the preform in response to the evacuation of the volume. According to this solution the preform is transferred over a small gap between the front face of the preform, arranged in the carrier of the first post-mold device, and the sealing surface of the molded article picker.
Although the above solution already constitutes a substantial improvement with respect to the prior art it has been found that in practice the transfer of the molded article from a carrier to the molded article picker sometimes fails. It is believed that this improper transfer is caused by an insufficient vacuum applied and the air flow resulting therefrom to transfer the molded article across the gap between the front face of the molded article and the sealing surface of the molded article picker. This occurs especially with molded articles having a shallow draft on the outside thereof. Consequently, it can happen that molded articles are not transferred properly, i.e. are left in the carrier, and, thus, block this carrier for the introduction of a molded article of the next shot of molded articles, which for obvious reasons is highly undesirable.
There is, thus, a need for a molded article picker providing for an improved reliability of transfer of a molded article from a carrier on a first post-mold device to such a molded article picker on a second post-mold device.